Heater for electron discharge devices



Dec. 6, 1932. H. L. CROWLEY HEATER FOR ELECTRON DISCHARGE DEVICES Filed Sept. 16. 1950 Patented Dec. 6, 1932 UNITED STATES HENRY L. CROWLEY, OF EAST ORANGE, NEW JERSEY, ASSIG-NOR T0 L. CROWLEY & COMPANY, INC., OF WEST ORANGE, NEW JERSEY, ACORPOBAT'ION OF NEW JERSEY HEATER non ELECTRON nrscnanen nnvrons Application filed September 16, 19,30.- Serial No; 482,275.

This invention relates to heater methods and with particularity to a novel type of heater element for audions andelectron discharge devices generally.

An object of the invention is to provide a heater for a so-called indirectly heated cathode which has a minimum of heat inertia.

A feature of the invention relates to an insulator member for so-called indirectly heated cathodes which member has a minimum of loss per unit of heat radiating surface.

Another feature of the invention relates to a ceramic insulator member for indirectly heated cathodes in the form of a flattened ceramic member having one or more bores to receive a heater filament. 7

Another feature of the invention relates to a heater element for indirectly heated cathodes comprising a flattened ceramic spacer element and a cylindrical sleeve surrounding said element.

Other features and advantages not specifi cally enumerated will be apparent after a consideration of the following detail descriptions and the appended claim.

Referring to the drawing:

Figure 1 shows in perspective view a novel type of insulating spacer according to the invention;

Fig. 2 shows an electron emitting cathode incorporating the spacer element of Figure 1.

Referring more particularly to Fig. 1, there is shown a block or slab 1 of insulating material, preferably in the form of an extruded ceramic prepared in accordance with the disclosure of application Serial No. 332,555, and having a transverse cross section of which the length a is a plurality of times greater than the width b with the ends rounded as shown. The insulating block 1 is provided with a pair of longitudinal bores 2 through which is looped a hair-pin filament or heating wire 3. The wire 3 may be of any suitable metal, but preferably is of a materialselected in accordance with the disclosure of application Serial No. 413,174. Thus for example the wire 3 may be of tungsten and-the block 1 may be of magnesia or other material which has a minimum of electrical reaction with the wire at elevated temperatures. In accordance with standard practice the insulator spacer member 1 is surrounded with a metallic sleeve or sheath 4: which carries the electron emissive' coating 5.

Because of the shape of the insulator shown in Fig. 1 there is less material required for the same degree of insulation as is required where a circular twin bore insulator tube is employed. Due to the lessened mass of the block as compared with the usual circular, cylindrical spacer, there is less heat inertiaand consequently when the heater is embodied in an electron discharge device there is a minimum of time lag between the application of currents to the wires 3 and the active emission from the electron coating 5. While the metal sleeve used in connection with the PATEN. OFFI E block 1 may be of the same shape, namely substantially in the form of a rectangular cylin-v der, as shown in Fig. 1, with rounded ends,

shown having a transverse length a of ap proximately 0.06 and a width b of approximately 0.025", thus reducing the mass of the insulator block by over half, as compared with the usual cylindrical block of circular cross section.

It has been found that'the substantially fiat shaped block shown is capable of easier and more accurate extrusion, and is liable to a smaller number of rejects during the extrusion operation than is the case with the circular block usually employed.

WVhile one specific shape for the insulating block is shown, it will be understood that the invention comprises Within its scope other shapes of blocks wherein the transverse length is materially greater than the transverse Width.

Other changes and modifications may be made Without departing from the spirit and scope of the invention.

\Vhatis claimed is:

A cathode structure comprising a substantially rectangular block of insulating material having its vertical edges of curved form in crosssection, a circular sleeve surrounding said block and contacting with its curved edges leaving a free space on each side of the block bounded by the sleeve, an electron emissive coating on said sleeve, and a heater element passing through said block.

In testimony whereof I'have hereunto set my hand on this 15th day of September A. D.,

HENRY L. OROVVLEY. 

